Chemical process



Patented Mar. 26, 1946 CHEMICAL PROCESS Hans c. Vesterdal, Elizabeth, N.1., mum: to

Standard Oil Development Company, a corporation of Delaware No Drawing.Application September 17, 1943. Serial No. 502,791

4 Claims.

This invention relates to the production oi higher molecular weighthydrocarbons from lower molecular weight hydrocarbons and, moreparticularly, to an improvement in the production of hydrocarbonsboiling in the gasoline range from normally gaseous hydrocarbons.

It is known that normallygaseous unsaturated hydrocarbons may beconverted to normally liquid hydrocarbons by treatment at elevatedtemperatures with or without catalysts and both with and without highsuperatmospheric pressure. Inparticular, it is known that propylene maybe condensed into liquid hydrocarbons boiling mainly in the gasolinerange by heating this olefin to a temperature between 700 and 900 F.under a pressure between 500 and 15,000 lbs/sq. in. for a short time.

One object of this invention is the conversion of gaseous hydrocarbonsinto high quality liquid hydrocarbons useful as motor fuels.

Another object is to effect the transformation or polymerization in aneconomical manner by the action of catalysts under high pressure.

Another object of this invention is to produce a high yield of lowboiling hydrocarbon liquids boiling in the gasoline range and havinggood anti-knock rating and high blending value.-

Qther objects will be apparent from the detailed discussion whichfollows.

A specific embodiment of the invention comprises treatingnormallyigaseous olefin hydrocar- The present process is particularlydirected to the production of dimers and trimers from monoolefins,particularly those oleflns whose lower polymers boil at temperatureswithin the approximate range of commercial motor-fuel, that is between100 and 400 F. It has been found that the dimers and some or the trimersof propylene,

for example, boil within this range and furthermore that these compoundshave unusually high antiknock characteristics.

The main feature or the present invention which stands asan improvementin the art 01' polymerizing gaseous olefins by catalysts and, moreparticularly, by oxide catalysts exemplified by chromium oxide depositedon alumina con sists in the use of regulated amounts of water or steamin the gas mixture undergoing polymerization. When passing a dry gasmixture containing about 95% propylene over a catalyst composed ofchromium oxide deposited on alumina at a temperature between 775 and 785F. and at an average pressure of about 2200 lbs/sq. in., the yield ofliquid products was 65.5 weight percent based on total feed and 70.2weight percent based on propylene consumed. Upon adding 0.25 mol percentof steam to the feed, the corresponding yields were 76.4 and 84.2 weightpercent,

respectively, and on adding 1.4 mol percent steam to the feed, thecorresponding yields were 80.5 and 89.0%. respectively. At a somewhathigher pressure, 2800 lbs/sq. in., the yields were 88.2 and 94.? weightpercent on total feed and olefin consumed, respectively, when adding 1.4mol percent steam to the feed.

Similar improvements in yields on addition of steam were also noticedwhen operating without catalyst. The data thus obtained are summarizedin the following table: I

Propylene condensation 1 Feed Propylene, 95% pure I CatalystOhromia-slumina N0 catalyst Run N0. 768- 99 89 97 103 107 Reaction time"70 132 134 30 144 70 70 70 Temp 785 776 780 785 785 785 775 790.Pressure 2, 200 1, 900 2, 800 2, 200 2,000 2, 200 2, 300 2, 200 IO/CrHqratio X100 0. 25 1. 4 1. 4 0. 31 0 0. 3 2. 9 11- 8 Yield of liquidproduct, wt. perce 1. Based on total iced 76. 4 80. 5 88, 2 73. 7 56. 269. 7 73.0 00. 1 2. Based on CgH. consumed 84.2 89.0 94. 7 82.0 60. 674.6 78.7 75. l Gasoline cut (-400 R), 'wt. percent in liquid 01. l 50.0 55. 0 59. 2 02. 4 59. 0 64. 8 6B. 5 Composition of gas. cut:

Oleflns 26 32 30 31 20 22 24 23 Aromatics... 7 3 5 6 l9 l0 5 l2Naphthenes 32 33 28 33 43 87 41 33 I Parafilns --do-- 20 35 32 37 30 1831 30 32 The polymerizing of gaseous oleflns of the yields of liquidhydrocarbons boiling in the motor present character may be brought aboutunder fuel range.

,products is very high when operating at or above certain pressuresdepending on the temperature of operation. Thus, when operating withoutcats alyst at 775 F. a high rate of reaction starts when the pressure israised to 2400-2600 lbs/sq. in. At 860' F. the pressure for highreaction rate is about 1200 lbs/sq. in. When operating at or above suchpressures, a reaction time of less than b one minute is necessary forpractically complete condensation. When using a chromia-alumina catalystthe pressure for high reaction rate is several hundred pounds per squareinch lower than when no catalyst is present, provided the temperature isheld between about 750 F. and 850 F. When operating without catalyst thepressures for high reaction rate at various temperatures are as follows:

Temperature, F.

Pressure for high reaction rate,

lbs/sq. lIl. .i.... 3, 100 2. 700 1, (I 1, (Hi0 In order to produce highyields of normally saturated hydrocarbons, it is preferred to hold thereaction temperature between about 775 and 800 F. and the pressure at orabove the high reaction rate pressure, that is, at or above 2400 lbs/sq.in. when operating at 775 F. and 2100 lbs/sq. in. when operating at 800F. At the same time. from 0.2 to about mol percent of steam should beadded to the propylene feed. The reaction is preferably carried out in acontinuous flow system and at contact times between about /2 and 180minutes.

Higher and lower temperatures may be used, but when operating attemperatures below 750 F. the product is generally more unsaturated. Attemperatures above 850 F. short contact times must be employed in orderto prevent carbon formation.

' liquid hydrocarbons which comprises subjecting From the above data itwill be seen that with the gas mixture applied the optimum percentage ofsteam is somewhat between 0.25 and 1.4 mol percent. This percentage willnecessarily be varled in case of gas mixtures containing variouspercentages of higher oleflns and will also be in.- fluenced by thetemperature and pressure found most suitable for the economical removalof olefin from diflerent cracked gas mixtures by the present process.

The reason why higher yields are obtained when small amounts or steamare added to the feed is not quite clear and it is not intended to limitthe present invention by claiming the theory involved but for the sakeoi! clarity it may be said that it has been found that the residual gasis more saturated when no steam is present, indicating that thepropylene has been hydrogenated to form propane which is not nearly asreactive as the propylene in the condensation reaction. The nature andobjects of the present invention having thus been set forth and specificexamples of the same given, what is claimed as new and useful anddesired to be secured by Letters Patcut is:

1. A process for the conversion oi propylene to propylene totemperatures between 775 and 800 F. and to high pressures in thepresence of from 0.25 to 5 mol percent of steam and a catalystcomprising chromium oxide and alumina.

2. A process for the conversion of propylene to liquid hydrocarbonswhich comprises subjecting propylene to a temperature between 775 and800 F. and a pressure between 2100 and 2400 lbs./sq. in. in the presenceof from 0.25 to 5 mol percent of steam and a catalyst comprisingchromium oxide and alumina.

3. A process for the conversion of propylene to liquid hydrocarbonswhich comprises subjecting propylene to a temperature of 775 and apressure of 2400 lbs/sq. in. and in the presence of 0.25 to 1.4 molpercent of steam and a catalyst comprising chromium oxide and aluminafor a contact time between 0.5 and 180 minutes.

4. A process for the conversion of propylene to liquid hydrocarbonswhich comprises subjecting propylene to a temperature of 800 F. and apressure of 2100 lbs/sq. in. and in the presence of 0.25 to 1.4 molpercent of steam and a catalyst comprising chromium oxide and aluminafor a con-' tact time between 0.5 and 180 minutes.

HANS G. VESTERDAL.

